Electronic counting circuits



p 11, 1962 D. WEIGHTON 3,054,021

ELECTRONIC COUNTING CIRCUITS Filed April 14, 1960 V R I RESET 3 INPUT l V3 L R6 E 0 HI COUNT v 0 INPUT i O" I11 OUTPUT OUTPUT Inventor D. \g/HGHTO/V y MM, W

United States Patent Otlice 3,054,021 ELECTRGNIC CGUNTING (IIRCUHTS Donald Weighton, Cambridge, England, assignor to Pye Limited, Cambridge, England, a British company Filed Apr. 14, 1960, Ser. No. 22,192 Claims priority, application Great Britain Apr. 20, 1959 9 Claims. (Cl. 31584.5)

The present invention relates to electronic counting circuits employing cold cathode gas discharge tubes having an anode, a cathode and at least one trigger electrode. Such counting circuits are known in the art and may take various forms, for example they may be in the form of a simple binary counter, or a ring counter. The anode of each counting tube is generally connected to the positive terminal of a high tension supply and the cathode is connected to the negative terminal of the supply, whilst pulses to be counted are applied to the trigger electrode of one or more of the tubes. Generally the anodes of the tubes are are connected to the positive terminal of the supply through a common series resistor which drops the voltage applied to the anode so that the potential existing between the anode and cathode of each tube is insufficient to cause the tube to strike, but so that any tube can strike by the application of a pulse of sutiicient amplitude to its trigger electrode.

In order to obtain efiicient and reliable striking of all of the tubes in the circuit during counting, it is desirable to have fairly consistent cathode potentials for all of the tubes and this cathode potential depends to a great extent on individual component tolerances and tube characteristics. It is possible to effect some improvement by increasing the value of the common series resistor which will make variations in the circuits associated with individual tubes less effective but it is then necessary to raise the HT. supply proportionately. In such a case, when the equipment is switched on and no tube is conducting, so that there is no potential drop across the common series resistor, this increased voltage appears at each tube anode and may cause tubes to strike which will upset the counter arrangement. Thus, if two tubes strike together it is impossible to count further as the normal manner of operation of the circuit in which the striking of one tube extinguishes any other tube can no longer be carried out. A further problem that exists is to ensure that one tube is struck when the circuit is switched on and for predictable counting it must be arranged that this is the tube which gives zero output. This has previously been achieved by fitting a switch which is manipulated after switching on the equipment and arranged to cancel all the tubes and then cause the zero tube to strike.

According to the present invention an electronic counting circuit employing cold cathode gas discharge tubes, is provided with a starter tube which operates upon switching on the circuit to ensure that there is only an output from the tube which gives zero output and that all other tubes are non-conducting. This can be achieved even with the use of a sufliciently high I-LT. potential to ensure definite counting.

According to a feature of the invention the starter tube also functions as a resetting arrangement. This may be achieved by applying a positive pulse to its trigger electrode which causes all of the counter tubes to be extinguished and produces the output potential at the cathode of. the zero tube.

The starter tube may have its cathode directly connected to the cathode of the zero tube and its anode connected to be fed through the common series resistor for all of the tubes. The trigger electrode of the starter tube is preferably connected to an intermediate point on a potential divider connected across the high tension supply.

In order that the invention may be more fully understood reference will now be made to the accompanying drawing which illustrates a circuit diagram of one embodiment of electronic counting circuit according to this invention.

Referring to the drawing, the circuit basically consists of two cold cathode gas discharge tubes V1 and V2 arranged to form a simple binary counter. Although a binary counter has been shown for the sake of simplicity it will be understood that the counter ring may comprise more tubes, as desired. The tube anodes are connected to the positive terminal and the cathodes to the negative terminal of a high tension supply source. If it is assumed that the potential across the tubes is not sufiicient to cause them to conduct then no current will flow until a positive potential is applied to one of the trigger elec trodes. If a positve pulse of sufficient amplitude is applied -to the trigger electrode of tube V1, then this tube will strike and current will flow between cathode and anode and capacitor 01 will begin to charge up. The voltage drop across the tube V1 is approximately constant, and this means that at the instant of striking, the potential at the anode of this tube will drop from RT. potential down to this value due to the presence of series resistor R1, and this potential is low enough to extinguish any other tubes, say tube V2, which have been conducting and now have a positive potential at the cathode due to the charge in the appropriate cathode capacitor (C2 in this case). The newly conducting tube V1 will charge 01 until a steady potential is achieved, with the HT. potential divided across the load resistor R1, the tube and the cathode resistor R2. The trigger electrode of tube V2 is connected via a resistance R3 to the cathode of tube V1 and the application of a small positive pulse at this trigger electrode after C1 is fully charged will now be sufficient to strike tube V2, which will act in a similar manner to extinguish tube V1 and charge C2. When C2 is charged the next trigger in the circuit (inthis case tube V1) is primed and this tube is ready to be fired by a suitable pulse. A resistor R2 is connected across capacitor C2 and, the trigger electrode of tube V1 is connected to the cathode of tube V2 through a resistor R3.

Let it be assumed that the tubes have approximately volts drop from anode to cathode and that an anode potential of about 300 volts will cause a tube to strike without being triggered, but with a lower voltage at the anode of say 200 volts, a pulse in excess of volts at the trigger will cause it to strike. The cathode circuit of e the tubes is arranged to stabilise at 100 volts, which raises the following trigger to this potential, and only requires a pulse in excess of 30 volts to fire the tube. A pulse in the region of 90 volts may actually be used. The small resistor R4, R4 in series with the anode of tubes V1 and V2 respectively is employed to ensure more positive firing, as with the common high tension positive line at 200 volts striking may not be completely reliable. inserting these series resistors the high tension positive line can be slightly higher in potential, so that the anode is at a higher potential when the tube is not conducting, but drops to a normal 200 volts when a tube strikes, due to the potential drop across this resistor.

For efficient and reliable firing of the tubes during counting it is desirable to have fairly consistent cathode potentials throughout, and this potential depends to a to raise the HT. potential proportionately. In addition,

Patented Sept. 11, 1962 3 upon switching on and when no tube is conducting so that there is no potential drop across R1 this increased voltage appears at each tube anode and may cause some tubes to strike, which will upset the counter arrangement as previously described.

According to this invention a starter tube V3 is provided which automatically functions at switching on to ensure that there is only an output at the cathode of the zero tube V1 and all other tubesare not conducting, even though a sufiiciently high H.T. potential is being used to ensure definite counting. The tube V3 also functions as a resetting circuit, and the application of a positive pulse to its trigger electrode causes all of the counter tubes to extinguish and then gives the output potential at the cathode of the zero tube V1.

The cathode of the starter tube V3 is connected directly to the cathode of the tube V1 whilst the trigger electrode is connected to a potential divider R5, R6 across the high tension supply. Upon switching on, the tube V3 will strike because of the potential at the trigger electrode, say 175 volts, the cathode being at negative potential. This causes the common high tension positive line to drop to about 100 volts, suflicient to extinguish any tube that happened to strike. The cathode capacitor C1 then slowly charges up until it reaches 100 volts, while the trigger electrode will now be at half the potential of the common high tension positive line, that is 100 volts. The starter tube cathode is directly connected to the zero tube cathode, and as the outputs are taken from the tube cathodes, it is clearly equivalent to the zero tube V1 itself as far as other associated circuitry is concerned. It counting pulses are now applied, the counter will act as explained above. With the first pulse the trigger electrode of tube V2 which is at 100 volts potential, will rise to 190 volts and tube V2 will strike which will extinguish the starter tube S, and eventually raise the trigger electrode of tube V1 to 100 volts. When it is required to reset the circuit a pulse is applied via the reset connection to the trigger electrode of the starter tube V3, which is at 100 volts potential, and it will then strike to extinguish all the other tubes and produce an output potential of 100 volts at the cathode of the zero tube V1.

Whilst a particular embodiment has been described it will be understood that various modifications may be made Without departing from the scope of this invention.

I claim:

1. In an electronic counting circuit comprising a plurality of cold cathode gas discharge tubes each having an anode, a cathode and a trigger electrode, a direct current source, means for applying a positive potential from said direct current source through a common resistor to the anodes of said tubes, circuit means connected to the cathodes and triggers of said tubes and interconnecting said tubes to form a counting circuit and means for applying pulses to be counted to said tubes; the improvement which comprises the inclusion in the circuit of an additional cold cathode gas discharge tube having an anode, a cathode and a trigger electrode, and which operates upon switching on the counting circuit to ensure that there is only an output from the counting tube which represents zero and that all other tubes are non-conducting.

2. An electronic counting circuit as claimed in claim 1, in which the additional tube also functions as a resetting arrangement for resetting the counter to the state at which an output potential is obtained from the zero tube.

3. An electronic counting circuit as claimed in claim 2, in which resetting ofthe counter is achieved by applying a positive pulse to the trigger electrode of the additional cold cathode gas discharge tube.

4. An electronic counting circuit as claimed in claim 1, in which the starter tube has its cathode directly connected to the cathode of the zero tube; e

5. In an electronic counting. circuit comprising a plu-.

rality of cold cathode gas discharge tubes each having an anode, a cathode and a trigger electrode, a direct current 4 source, means for applying a positive potential from said direct current source through a common resistor to the anodes of said tubes, circuit means connected to the cathodes and triggers of said tubes and interconnecting said tubes to form a counting circuit and means for applying pulses to be counted to said tubes; the improvement which comprises the inclusion in the circuit of an additional cold cathode gas discharge tube having an anode, a cathode and a trigger electrode, and means for applying potentials to said additional tube upon switching on the circuit to ensure that said additional tube strikes, whereby said additional tube operates to insure that all the counting tubes are non-conducting and a particular counting tube is conditioned to be first operative upon the receipt of counting pulses.

6. In an electronic counting circuit comprising a plurality of cold cathode gas discharge tubes each having an anode, a cathode and a trigger electrode, a direct current source, means for applying a positive potential from said direct current source through a common resistor to the anodes of said tubes, circuit means connected to the cathodes and triggers of said tubes and interconnecting said tubes to form a counting circuit and means for applying pulses to be counted to said tubes; the improvement which comprises the inclusion in the circuit of an additional cold cathode gas discharge tube having an anode, a cathode and a trigger electrode, means connecting the anode of said tube to said common resistor, means connecting the cathode of said tube to an electrode of one of said counting tubes, a potential divider connected across said D.C. source and means connecting the trigger electrode of said additional gas discharge tube to an intermediate point on said potential divider whereby said additional tube operates upon switching on the circuit to ensure that all the counting tubes are non-conducting and a particular counting tube is conditioned to be first operative upon the receipt of counting pulses.

7. In an electronic counting circuit as claimed in claim 6, means for applying resetting pulses to the trigger electrode of said additional tube to reset the counter to its initial state.

' 8, An electronic counting circuit comprising a plurality of cold cathode gas discharge tubes each having an anode, a cathode and a trigger electrode, a direct current source, means for applying a positive potential from said direct current source through a common resistor to the anodes of said tubes, circuit means connected to the cathodes and triggers of said tubes and interconnecting said tubes to form a counting circuit, means for applying pulses to be counted to said tubes, an additional cold cathode gas discharge tube having an anode, a cathode and a trigger electrode, means connecting the anode of said tube to said common resistor, means connecting the cathode of said tubeto the cathode of that one of said counting tubes which represents zero, a potential divider connected across said "D.C. source and means connecting the trigger electrode of said additional gas discharge tube to an intermediate point on said potential divider whereby said additional tube operates upon switching on the circuit to ensure that all the counting tubes are non-conducting and an output is produced representing zero count.

9. An electronic counting circuit comprising a plurality of cold cathode gas discharge tubes each having an anode, a cathode and a trigger electrode, a direct current source, means for applying a positive potential from said direct current source through a common resistor to the anodes of said tubes, circuit means connected to the cathodes and triggers of said tubes and interconnecting said tubes to form a counting circuit, means for applying pulses to be counted to said tubes, an additional cold cathode gas discharge tube having an anode, a cathode and a trigger electrode, means connecting the anode of said tube to said common resistor, a connection from the cathode of said tube to an electrode of one of said counting tubes, a potential divider connected across said D.C. source and means connecting the trigger electrode of said additional gas discharge tube to an intermediate point on said potential divider whereby said additional tube operates upon switching on the circuit to ensure that all the counting tubes are non-conducting and a particular tube is conditioned to be first operative upon the receipt of counting pulses.

References Cited in the file of this patent UNITED STATES PATENTS Gulden July 18, 1950 Acton Dec. 10, 1957 Geisler June 3, 1958 Davidson et a1. Oct. 20, 1959' 

